It is sometimes necessary to remove one or more vertebrae, or a portion of the vertebrae, from the human spine in response to various pathologies. For example, one or more of the vertebrae may become damaged as a result of tumor growth, or may become damaged by a traumatic or other event. Excision of at least the generally anterior portion, or vertebral body, of the vertebra may be referred to as a corpectomy. An implant is usually placed between the remaining vertebrae to provide structural support for the spine as a part of a corpectomy. FIG. 1 illustrates four vertebrae, V1-V4 of a typical lumbar spine and three spinal discs, D1-D3. As illustrated, V3 is a damaged vertebra and all or a part of V3 could be removed to help stabilize the spine. If removed along with spinal discs D2 and D3, an implant may be placed between vertebrae V2 and V4. Most commonly, the implant inserted between the vertebrae is designed to facilitate fusion between remaining vertebrae. Sometimes the implant is designed to replace the function of the excised vertebra and discs. All or part of more than one vertebrae may be damaged and require removal and replacement in some circumstances.
Many implants are known in the art for use in a corpectomy procedure. One class of implants is sized to directly replace the vertebra or vertebrae that are being replaced. Another class of implants is inserted into the body in a collapsed state and then expanded once properly positioned. Expandable implants may be advantageous because they allow for a smaller incision when properly positioning an implant. Additionally, expandable implants may assist with restoring proper loading to the anatomy and achieving more secure fixation of the implant. Implants that include insertion and expansion mechanisms that are narrowly configured may also provide clinical advantages. In some circumstances, it is desirable to have vertebral endplate contacting surfaces that effectively spread loading across the vertebral endplates. Effective implants should also include a mechanism for maintaining the desired positions, and in some situations, being capable of collapsing. Fusion implants with an opening may also be advantageous because they allow for vascularization and bone growth through all or a portion of the implant.
Expandable implants may also be useful in replacing long bones or portions of appendages such as the legs and arms, or a rib or other bone that is generally longer than it is wide. Examples include, but are not limited to, a femur, tibia, fibula, humerus, radius, ulna, phalanges, clavicle, and any of the ribs.